The current ISS oxygen recovery method utilizes the Sabatier process which is only 50% efficient due to limits on H2 availability. This means that for a full crew over 3 kg of water/day are used in making oxygen that isn't recovered from CO2. At current launch prices this costs up to $100,000/day, depending on the provider.

By producing a self-cleaning Boudouard reactor the single greatest challenge of the Bosch process is resolved and the full oxygen recovery of the system can be realized. The decrease in consumable requirements will be significant for the ISS and enabling for deep space exploration missions. In addition, oxygen production is a limiting factor in ISS population and a system such as this can help improve that number.

For deep space exploration missions, in-space resupply is virtually impossible so nearly 100% oxygen recovery is essential to reduce the Initial Mass in Low Earth Orbit (IMLEO). The graphite/carbon nanotube “soot” product could have applications in air or water purification filters and as a filler for 3D printing.

Oxygen recovery from respiratory CO2 is an important aspect of human spaceflight. Methods exist to sequester the CO2­, but production of oxygen needs further development. The current ISS Carbon Dioxide Reduction System (CRS) uses the Sabatier reaction to produce water (and ultimately breathing air). Oxygen recovery is limited to 50% because half of the hydrogen used in the Sabatier reactor is lost as methane, which is vented overboard. The Bosch reaction is the only real alternative to the Sabatier reaction, but in the last reaction in the cycle (Boudouard) the resulting carbon buildup will eventually foul the nickel or iron catalyst, reducing reactor life and increasing consumables. To minimize this fouling, find a use for this waste product, and increase efficiency, we propose testing various self-cleaning catalyst designs in an existing MSFC Boudouard reaction test bed and to determine which one is the most reliable in conversion and lack of fouling. Challenges include mechanical reliability of the cleaning method and maintaining high conversion efficiency with lower catalyst surface area. The above chemical reactions are well understood, but planned implementations are novel (TRL 2) and haven’t been investigated at any level.

Tests of our first self-cleaning prototype reactor in December 2015 were very encouraging. The 1-inch ID reactor produced CO2 and carbon at an ever-increasing rate during a 12-hour run with no sign of clogging of the reactor. After the test, we found that a large fraction of the carbon formed had been removed during the run and that the flow path was open. The conversion of CO into CO2 and carbon was nearly half the maximum possible. Tests are planned soon with a 2-inch ID reactor with four times the throughput of the 1-inch reactor, but with a smaller reactor mass.",
"files": "",
"id": 27915,
"title": "Recent Results",
"type": "Story"
},
{
"description": "Two-Step Bosch Process Diagram",
"files": {"file": {
"size": 44074,
"id": 16567,
"url": "https://techport.nasa.gov/file/16567"
}},
"id": 21749,
"title": "Two-Step Bosch Process Diagram",
"type": "Image"
}
]},
"technologyMaturityStart": 2,
"responsibleMissionDirectorateOrOffice": "Space Technology Mission Directorate",
"id": 32720,
"startDate": "Apr 2015",
"status": "Completed"
}}